Gas-blast circuit interrupter with magnetic means for accelerating merger of series-related arcs

ABSTRACT

Discloses a gas-blast circuit breaker comprising two spacedapart stationary contacts and a movable bridging contact extending therebetween. The bridging contact has an arc-running surface facing the space between the stationary contacts and a centrally located gap that divides the arc-running surface into two spaced-apart sections. Two slots in the bridging contact extend in opposite directions from the gap generally parallel to and behind the arc-running surface. This configuration of the bridging contact is such that the current paths through the two arcs formed upon contact separation are of such configuration that magnetic forces are developed for driving the arcs together and accelerating their merger into a single arc.

United States Patent [72] Inventor William H. Rathbun Pittsfield, Mass. [21] Appl. No. 820,461

[22] Filed Apr. 30, 1969 [45] Patented May 25, 1971 [73] Assignee General Electric Company [54] GAS-BLAST CIRCUIT INTERRUPTER WITH MAGNETIC MEANS FOR ACCELERATING MERGER OF SERIES-RELATED ARCS [56] References Cited UNITED STATES PATENTS 2,208,387 7/1940 Pierce- 200/147X 2,918,552 12/1959 Fust 200/147 3,133,176 5/1964 Schneider... ZOO/148(2) 3,471,666 10/1969 Barkan 200/ l 48( .2)

ABSTRACT: Discloses a gas-blast circuit breaker comprising two spaced-apart stationary contacts and a movable bridging contact extending therebetween. The bridging contact has an arc-running surface facing the space between the stationary contacts and a centrally located gap that divides the arerunning surface into two spaced-apart sections. Two slots in the bridging contact extend in opposite directions from the gap generally parallel to and behind the arc-running surface. This configuration of the bridging contact is such thatthe current paths through the two arcs formed upon contact separation are of such configuration that magnetic forces are developed for driving the arcs together and accelerating their merger into a single arc.

- PATENTEDmwzsmn I 3.581.035

INVENTOR. WILL/AM RATHBUN, 5) 5 m ATTORNEY GAS-BLAST CIRCUIT INTERRUIIER WITI-I MAGNETIC MEANS FDR ACCELERATING MERGER F SERIES- RELATED ARCS This invention relates to a circuit interrupter of the gas-blast type, and, more particularly, relates to a circuit interrupter of this type in which a pair of series-related arcs are initially drawn, and these arcs, under the influence of a gas blast, are forced to merge into a single are that is acted upon by the gas blast.

An example of an interrupter of this type is the resistor switch shown and claimed in US. Pat. No. 3,l33 ,l76S chneider, assigned to the assignee of the present invention. There are two spaced-apart stationary contacts (73 and 76) are provided to define an arcing space therebetween. A bridging contract ('78) normally engages the stationary contacts at a pair of spaced contact-making points to carry current between the stationary contacts. During a switch-opening operation, the bridging contact is moved radially outward of the arcing space to form two series-related arcs at the contactmaking points. Under the influence of the gas blast that is then flowing through a passage (100) in one of the stationary contacts, these arcs move toward each other and merge into a single'arc between the stationary contacts. The single arc is soon extinguished by the action of the gas blast, thereby completing the interrupting operation.

An object of my invention is to accelerate the merger of the two spaced-apart arcs into a single are so as to shorten the time required to extinguish the single arc and complete the interrupting operation.

In carrying out my invention in one form, I form the bridging contact as elongated member having a relatively long dimension extending between the two bridged contacts and a relatively short dimension extending generally circumferentially of the blast passage through one of the bridged contacts. The bridging contact has an arc-running surface facing the arcing space between the bridged contacts and a centrally located gap that divides the arc-running surface into two spaced-apart sections. Two slots are provided in the bridging contact extending inopposite directions from said gap generally parallel to and behind the arc-running surface to end locations past the contact-making points on the bridging contact, thereby forming a pair of arms each extending from an outer edge of the bridging contact to said gap and each being spaced along its length from the remainder of the bridging contact. When arcs are formed on the arms by opening movement of the bridging contact, the current flowing to each arc through the bridging contact flows from the outer edge of the contact through the arm on which the arc is located, thereby developing magnetic forces on the arcs that urge them together.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view partly in section showing an interrupted embodying one form of my invention. The interrupter is shown in closed position.

FIG. 2 is a side elevational view similar to that of FIG. 1 except showing the interrupter in a partially open position.

FIG. 3 is an enlarged view during an opening operation of the bridging contact forming a portion of FIG. 1.

FIG. 4 is a view along the line 44 of FIG. 1.

FIG. 5 is an enlarged end view of the bridging contact of FIG. 3 looking in' the direction ofarrow 8.

FIG. 6 is a sectional view along the line 6-6 of FIG. 5.

Referring now to FIG. 1, there is shown a gas-blast circuit interrupting device comprising a pair of stationary contacts 12 and I4 spaced apart by an arcing space 16. Contact 14 is a tubular member having a bore 18 defining a blast passage that leads from the arcing space. Contact I2 is mounted on an insulator 20, and current is carried to and from contact I2 by a terminal conductor 21.

For carrying current between the two stationary contacts 12 and 14, a movable bridging contact is provided. This 0 municates with another passage 32 that leads to a low-pressure region, such as atmosphere, via a suitable normally closed blast valve (not shown). When the interrupter is to open, the normally closed blast valve is opened, and a blast of gas is caused to flow from the tank interior to atmosphere. Referring to FIG. 2 this blast passes successively through arcing space 16, the bore 18, and passage 32, following paths such as shown by the dotted line arrows 35 and 39 as it traverses the arcing space.

Within the bore 18 is a downstream electrode 36 that is supported on a conductive rod 38 secured to the body of contact 14. Electrode 36 may be though of as being a part of contact 14. Electrode 36 is an annular disc that is generally concentric with and spaced from the bore 18 so that during an opening operation gas may flow around the outer periphery of the electrode 36 and into passageway 32 via paths such as depicted by arrows 39.

The interrupting device, as described up to this point, is similar to the interrupting device of the resistor switch shown in the aforesaid Schneider US. Pat. No. 3,133,176, and reference-may be had thereto if more information is desired to an environment in which this interrupting device can be used.

When bridging contact 25 is moved upwardly from its closed position of FIG. 1, two series-related arcs 40 and 41 are established at the contact-making points 27 and 28. These arcs, which are shown in FIGS. 2 and 3, are driven by the gas blast toward each other; and after a predetermined amount of such movement, they merge into a single arc, which appears at 43 (FIG. 2) between the stationary contact 12 and the downstream electrode 36. When the arc is in this position, it is subjected to effective cooling and deionizing by the gas blast, thus facilitating its extinction at an early current zero, thereby completing the interrupting operation.

The length of time required for the arcs 40 and 41 to merge into a single are appearing at 43 is directly dependent upon the speed at which they move toward each other from their initiation points 27 and 28. For accelerating this movement, I have constructed the bridging contact 25 in a special manner which results in magnetic forces being exerted on the arcs to urge them toward each other. More specifically, the bridging contact is an elongated barlike member that has its relatively long dimension extending between the stationary contacts and its short dimension extending generally circumferentially of the bore 18. Facing the arcing space 16 is an arc-running surface 50, which is divided into two spaced-apart sections by a centrally located gap 52. A pair of slots 54 extend in opposite directions from this gap 52 generally parallel to and behind the arc-running surface 50 to end locations 56 past the contact-making point 27 and 28. The bridging contact may be thought of as comprising a pair of arms 58 extending from the outer edges of the bridging contact to the gap 52 in spaced relationship along their length to the remainder of the contact.

The presence of these arms 58 forces any current flowing through an arc at 40 or 41 to follow a loop-shaped path which bows in the region of the arc toward the centrally located gap 52. The magnetic effect of current flowing through a path of this configuration is to lengthen the loop by forcing the arc toward the centrally located gap 52. This magnetic force varies in magnitude as a direct function of the current. Accordingly, there is a magnetic force on each arc varying directly with current and urging the arc toward the other arc. As explained previously, this accelerates movement of the arcs toward each other, thus causing them to more quickly merge into a single are appearing at 43.

ln the'interrupting device of the aforesaid Schneider patent, the-bridging contact is a generally hemispherical button. Instead of this hemispherical form, my button is an elongated member of bar form. This bar configuration is advantageous because it offers much less obstruction to flow of arc-extinguishing gasses through the arcing region, thus allowing a more effective blasting of the are at 43. The bar form of the bridging contact is advantageous also because it confines the current path adjacent the arcs 40 and 41 to locations in the bridging contact which are radially outward of each arc. If the bridging contact was hemispherical, this current path would be more diffuse and current would tend to approach the are from all directions instead of being confined to a radially inwardly extending pathextending generally perpendicular to said gap 52, which is the path most effective in producing a force for driving the arc toward the centrally located gap 52.

The slots 54 can be formed in any suitable manner. I prefer to form them by drilling a hole 60 through the contact transversely thereof and then milling or sawing each slot out with a tool inserted in the hole and moved generally parallel to the arc-running surface 50.

It is to be noted that the arc-running surface 50 as viewed in FIG. 6 is smoothlyrounded, thus helping to reduce dielectric stress concentrations adjacent the surface.

While 1 have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A circuit interrupter of the gas-blast type comprising:-

. a. a first contact,

b. a second contact spaced from said first contact to define an arcing space therebetween, said second contact being a generally tubular member having a bore defining a blast passage leading from said arcing space for directing an arc-cooling gas blast from said arcing space, c. a bridging contact having a closed position wherein it engages said first and second contacts, respectively, at a pair .of contact-making points to carry current between said first and second contacts,

d. said bridging contact being an elongated bar-shaped member having a relatively long dimension extending between said first and second contacts 1 and a relatively short dimension considered circumferentially of said blast passage when in closed position,

c. said bridging contact having an arc-running surface facing said arcing space and extending between said first and second contacts when in closed position,

f. said bridging contact including a centrally located gap that divides said arcing surface into two spaced-apart sections and also including a pair of slots that extend in opposite directions from said gap generally parallel to and behind said arc-running surface to end locations past said contact-making points on the bridging contact, thereby forming a pair of arms each extending from an outer edge of said bridging contact to said gap and each being spaced along its length by an associated one of said slots from the remainder of said bridging contact,

g. said bridging contact being movable radially outward of said arcing space during an opening operation to form arcs at said contact-making points,

h. current flowing to each of said arcs through said bridging contact following a path extending from an outer edge of said contact through the arm on which said are is located, thereby developing magnetic forces on said arcs that urge the arcs together,

i. said first, second, and bridging contacts normally being immersed in pressurized gas that flows in the form of said gas blast from the space enveloping said contacts through said arcing space and said blast passage during interruption,

j. said two arcs merging into a single are between said first and second contacts that is forced by said gas blast into a position wherein a portion of the single arc is within said blast passage and extends longitudinally thereof.

2. The circuit-interrupting device of claim 1 in which the contact-making point between said bridging contact and the tubular second contact is located immediately adjacent the entrance to said blast passage from said arcing space, said gas blast flowing from said arcing space into said blast passage during an interrupting operation, the arms of said bridging contacts being of a rounded configuration in the region facing said arcing space as viewed from transverse cross sections per pendicular to their length. 

1. A circuit interrupter of the gas-blast type comprising: a. a first contact, b. a second contact spaced from said first contact to define an arcing space therebetween, said second contact being a generally tubular member having a bore defining a blast passage leading from said arcing space for directing an arc-cooling gas blast from said arcing space, c. a bridging contact having a closeD position wherein it engages said first and second contacts, respectively, at a pair of contact-making points to carry current between said first and second contacts, d. said bridging contact being an elongated bar-shaped member having a relatively long dimension extending between said first and second contacts and a relatively short dimension considered circumferentially of said blast passage when in closed position, e. said bridging contact having an arc-running surface facing said arcing space and extending between said first and second contacts when in closed position, f. said bridging contact including a centrally located gap that divides said arcing surface into two spaced-apart sections and also including a pair of slots that extend in opposite directions from said gap generally parallel to and behind said arc-running surface to end locations past said contact-making points on the bridging contact, thereby forming a pair of arms each extending from an outer edge of said bridging contact to said gap and each being spaced along its length by an associated one of said slots from the remainder of said bridging contact, g. said bridging contact being movable radially outward of said arcing space during an opening operation to form arcs at said contact-making points, h. current flowing to each of said arcs through said bridging contact following a path extending from an outer edge of said contact through the arm on which said arc is located, thereby developing magnetic forces on said arcs that urge the arcs together, , i. said first, second, and bridging contacts normally being immersed in pressurized gas that flows in the form of said gas blast from the space enveloping said contacts through said arcing space and said blast passage during interruption, j. said two arcs merging into a single arc between said first and second contacts that is forced by said gas blast into a position wherein a portion of the single arc is within said blast passage and extends longitudinally thereof.
 2. The circuit-interrupting device of claim 1 in which the contact-making point between said bridging contact and the tubular second contact is located immediately adjacent the entrance to said blast passage from said arcing space, said gas blast flowing from said arcing space into said blast passage during an interrupting operation, the arms of said bridging contacts being of a rounded configuration in the region facing said arcing space as viewed from transverse cross sections perpendicular to their length. 